The present invention relates to air-to-air missiles and, in particular, it concerns methods for operating such missiles for targets outside the field-of-view of a radar system, or independent of the presence of a radar system.
The extremely high speed of modern air-to-air combat stretches the capabilities of a human pilot to their limits. Faced with complex aircraft instrumentation and high-tech weapon systems, a pilot is required to achieve split-second reaction times as supersonic aircraft pass each other at relative speeds up to thousands of miles per hour. Various high performance target-seeking air-to-air missiles have been developed to operate under these conditions. However, many factors generally limit the usefulness of such missiles to greatly less than their theoretical performance capabilities.
Specifically, and with reference to FIGS. 1 and 2, it should be noted that operation of air-to-air missiles is generally integrated with a radar system of an aircraft. A typical sequence of operation is illustrated in the left portion of FIG. 1 as follows. First, at step 10, the radar detects (acquires) a target and, usually under the control of the pilot, directs the seeker of the missile to track the target (step 12). Once both the radar and the missile seeker are locked-on to a target, the two tracking directions are typically displayed to the pilot superimposed on a display, thereby allowing the pilot to verify visually that the missile is successfully tracking the intended target (step 14). Advantageously, information about the target, such as range-derived data from the radar measurements and tracking direction information, together with predefined information regarding the performance limitations of the missile and flight data from the aircraft systems are processed to determine whether a number of criteria indicative of the capability of the missile to reach the target are satisfied (step 16). This information is typically represented graphically on a head-up-display (HUD) combined with data from the radar, allowing visual interpretation by the pilot of whether the target is within the maximum range and other performance limitations of the missile prior to firing.
Although the close integration of missile operation with the radar system provides very effective operation within the field-of-view of the radar, it also leads to severe limitations outside that range. Thus, as shown in the right portion of FIG. 1, target acquisition through the radar system is clearly not possible outside the field-of-view of the radar system (10xe2x80x2). In the event that a target is initially acquired by the radar system while within its field-of-view, the tracking of step 12 may continue outside the radar field-of-view (12xe2x80x2). However, the target verification is no longer available (14xe2x80x2) with the result that the pilot cannot be sure that the missile is in fact tracking the intended target. Similarly, the calculation of performance limitations criteria ceases (16xe2x80x2) as soon as the target leaves the radar field-of-view such that the pilot lacks all indications as to whether the missile is capable of reaching the intended target.
The significance of these limitation will be better appreciated with reference to FIG. 2. As shown here, the field-of-view 18 of the radar system of a combat aircraft does not generally extend more than 60xc2x0 above the boresight direction, and is frequently limited in practice to nearer 30xc2x0. In contrast, the field-of-view 20 of the seeker of a high performance air-to-air missile is generally much wider, in many cases lying in the 80xc2x0-90xc2x0 range. As a result, in very many cases, a target may be inaccessible despite being visible to the pilot and within the capabilities of the missile to track and destroy.
One example in which the large blind region of the radar system presents a critical limitation to operation of air-to-air missiles relates to what is known as the xe2x80x9cvertical modexe2x80x9d. A predominant course of action in air-to-air combat situations is for the pilot to pull the nose of the aircraft xe2x80x9cupxe2x80x9d (in the pilot""s frame of reference) so as to draw the nose towards a target. In this case, the target is generally visible to the pilot at a high angle above his head and, by continuing to pull the nose up, the pilot attempts to reduce this angle to bring the target more in front of him. A xe2x80x9cvertical modexe2x80x9d seeks to acquire a target located xe2x80x9cupwardsxe2x80x9d in the pilot""s frame of reference to allow the pilot to fire a missile at the earliest possible opportunity. However, a vertical mode based upon the radar system is once again limited to the low angle of inclination covered by the radar, thereby greatly delaying acquisition of the target.
One approach to facilitating target acquisition and verification outside the field-of-view of the radar system is by use of a helmet-mounted cueing system. This employs a magnetic or an optical system to monitor the position of a helmet provided with a helmet-mounted head-up display. In this case, in a cueing mode, the missile seeker is enslaved to follow an optical axis of the display which moves together with the helmet. Cueing is achieved by the pilot turning his head, and hence the helmet, to bring the optical axis into alignment with the target.
While providing a partial solution to the problem of target acquisition and verification, helmet-mounted displays and cueing systems suffer from a large number of disadvantages. Firstly, the components mounted in the helmet add greatly to the weight of the helmet This weight becomes multiplied numerous times under high-acceleration conditions, becoming a major source of fatigue and stress for the pilot. Secondly, these systems generally require alignment of the optical axis of the helmet with the target to be designated. Although this can be achieved over a range of angles beyond the radar field-of-view, operation of the system is still limited by the angular range of helmet motion which the pilot can achieve, which is typically smaller than the actual field of view both of the pilot and of the seeker. Furthermore, shifting of the entire head together with the heavy helmet to the required angle under high acceleration conditions may require great effort, and may cause significant delay in the cueing procedure. Thirdly, the helmet-mounted display typically requires very substantial connections between the helmet and other devices within the aircraft. These connections generally include a significant power supply and electrical and/or optical fibers for carrying projected information for the display. Such connections pose a significant safety hazard for the pilot, particularly with respect to emergency ejection where a special guillotine is required to sever the connections in case of emergency. The supply of a high voltage power line to within the helmet is also viewed as a particular safety hazard. Fourthly, the addition of helmet-mounted displays and cueing systems fails to provide any indication to the pilot regarding the capability of the missile to reach the target when the target lies outside the radar field-of-view. Finally, the integration of a head mounted display and cueing system into the aircraft systems is a highly expensive project, requiring adaptation of numerous subsystems, with all the complications of safety and reliability evaluation procedures and the like which this entails.
There is therefore a need for methods of operating an air-to-air missile which would allow effective operation of the missile with respect to targets lying outside the radar field-of-view, or altogether independent of a radar system, without requiring use of a helmet-mounted display. It would also be highly advantageous to provide a missile configured to provide effective modes of operation with respect to targets lying outside the radar field-of-view, or altogether independent of a radar system.
The present invention is a method for operating a short range, air-to-air missile, and a corresponding missile.
According to the teachings of the present invention there is provided, a method for operating a short range, air-to-air missile carried by an aircraft flown by a pilot, the missile having a seeker operative to track a target, the method comprising: (a) providing a first indication to the pilot when the seeker is tracking a target; and (b) providing a second indication to the pilot when a rate of angular motion of the seeker falls below a given value for a predefined period.
According to a further feature of the present invention, the first indication and the second indication are readily distinguishable audible signals.
There is also provided, according to the teachings of the present invention, a method for operating a short range, air-to-air missile carried by an aircraft flown by a pilot, the missile having a seeker configured to track a target, the method comprising: (a) providing a signaling unit associated with the missile and configured to provide a first indication to the pilot when the seeker is tracking a target and to provide a second indication to the pilot when a rate of angular motion of the seeker falls below a given value for a predefined period; and (b) while the seeker is tracking a target visible to the pilot, flying the aircraft in such a manner that the direction of a line of sight from the pilot to the target remains substantially constant in a frame of reference moving with the aircraft for the predefined period, thereby causing the signaling unit to generate the second indication.
There is also provided, according to the teachings of the present invention, a short range, air-to-air missile to be carried by an aircraft flown by a pilot, the missile comprising: (a) a gimbaled seeker configured to track a target; (b) a processing system including at least one processor, the processing system being configured to provide a first indication to the pilot when the seeker is tracking a target; (c) wherein the processing system is further configured to provide a second indication to the pilot when a rate of angular motion of the seeker falls below a given value for a predefined period.
There is also provided, according to the teachings of the present invention, a short range, air-to-air missile to be carried by an aircraft flown by a pilot, the missile comprising: (a) a gimbaled seeker configured to track a target, the gimbaled seeker having a direction of regard defined by an angle of inclination xcex8 from a predefined boresight direction and an orientation angle xcfx86 measured about an axis corresponding to the boresight direction, the angle of inclination xcex8 being limited by a predefined maximum angle xcex8max; and (b) a processing system including at least one processor associated with the seeker, the processing system being configured to: (i) process the angle of inclination while the seeker is tracking a target to derive a rate of change of the angle of inclination {dot over (xcex8)}, (ii) evaluate an off-boresight tracking angle limitation parameter as a function of both the angle of inclination and the rate of change, and (iii) generating a tracking angle exceedance signal when the off-boresight tracking angle limitation parameter falls outside a predefined range.
According to a further feature of the present invention, the processing system is configured to evaluate the off-boresight tracking angle limitation parameter P according to a relation P=xcex8+t0{dot over (xcex8)} where t0 is a predefined measure of time taken after firing for the missile to begin to turn, and wherein the processing system is configured to generate the tracking angle exceedance signal when P is greater than xcex8max.
According to a further feature of the present invention, the processing system is configured to generate the tracking angle exceedance signal as an electric signal corresponding to a distinctive audio output.
There is also provided, according to the teachings of the present invention, a short range, air-to-air missile to be carried by an aircraft flown by a pilot, the missile comprising: (a) a gimbaled seeker having a direction of regard defined by an angle of inclination xcex8 from a predefined boresight direction and an orientation angle xcfx86 measured about an axis corresponding to the boresight direction; and (b) a processing system including at least one processor associated with the seeker, the processing system being configured: (i) to selectively actuate the seeker to perform a scanning search pattern for a target, the scanning search pattern being confined to a range of orientation angles spanning no more than 20xc2x0 and covering a range of inclination angles spanning no less than 30xc2x0, and (ii) when a target is found, to cause the seeker to track the target.
According to a further feature of the present invention, the scanning search pattern covers a range of inclination angles spanning no less than 50xc2x0.
According to a further feature of the present invention, the angle of inclination xcex8 is limited by a predefined maximum angle xcex8max, the scanning search pattern covering a range of inclination angles extending substantially up to the predefined maximum angle xcex8max.
According to a further feature of the present invention, the scanning search pattern is confined to a range of orientation angles spanning no more than 10xc2x0, and preferably spanning between 5xc2x0 and 10xc2x0.
According to a further feature of the present invention, there are also provided attachment features configured to define an orientation of attachment of the missile to an aircraft such that, when attached to an aircraft, a given value of seeker orientation angle xcfx86v corresponds to a xe2x80x9cverticalxe2x80x9d direction in an aircraft frame of reference, wherein the scanning search pattern is confined to a range of orientation angles of xcfx86vxc2x15xc2x0.
There is also provided, according to the teachings of the present invention, a method for operating a short range, air-to-air missile carried by an aircraft flown by a pilot, the missile including a gimbaled seeker having a direction of regard defined by an angle of inclination xcex8 from a predefined boresight direction and an orientation angle xcfx86 measured about an axis corresponding to the boresight direction, the method comprising: (a) causing the seeker to perform a scanning search pattern for a target, the scanning search pattern being confined to a range of orientation angles spanning no more than 20xc2x0 and covering a range of inclination angles spanning no less than 30xc2x0, and (b) when a target is found, causing the seeker to track the target.
According to a further feature of the present invention, the scanning search pattern covers a range of inclination angles spanning no less than 50xc2x0.
According to a further feature of the present invention, the angle of inclination xcex8 is limited to a predefined maximum angle xcex8max, the scanning search pattern covering a range of inclination angles extending substantially up to the predefined maximum angle xcex8max.
According to a further feature of the present invention, the scanning search pattern is confined to a range of orientation angles spanning no more than 10xc2x0, and preferably spanning between 5xc2x0 and 10xc2x0.
According to a further feature of the present invention, the scanning search pattern is confined to a range of orientation angles of xcfx86vxc2x15xc2x0 where xcfx86v corresponds to a vertical direction in the aircraft frame of reference.
There is also provided, according to the teachings of the present invention, a method for operating a short range, air-to-air missile carried by an aircraft flown by a pilot, the missile including a gimbaled seeker having a direction of regard defined by an angle of inclination xcex8 from a predefined boresight direction and an orientation angle xcfx86 measured about an axis corresponding to the boresight direction, the angle of inclination xcex8 being limited by a predefined maximum angle xcex8max, the method comprising: (a) processing the angle of inclination while the seeker is tracking a target to derive a rate of change of the angle of inclination {dot over (xcex8)}; (b) evaluating an off-boresight tracking angle limitation parameter as a function of both the angle of inclination and the rate of change; and (c) generating a tracking angle exceedance signal when the off-boresight tracking angle limitation parameter falls outside a predefined range.
According to a further feature of the present invention, at least the steps of processing and evaluating are performed by a processing system located within the missile.
According to the teachings of the present invention, in an aircraft carrying a short range, air-to-air missile having a seeker configured to track a target within a missile field-of-view, the aircraft including a radar system which provides range-derived data relating to targets within a radar field-of-view smaller than the missile field-of-view, there is also provided a method for evaluating whether the missile will be effective in reaching a target comprising the steps of: (a) during a first period when a given target lies within the radar field-of-view, evaluating at least one performance limitation criterion relating to the ability of the missile to reach the given target, the performance limitation criterion being evaluated using the range-derived data for the given target; and (b) during a second period subsequent to the given target leaving the radar field-of-view, evaluating the performance limitation criterion using approximate range-derived data for the given target, the approximate range-derived data being derived by extrapolation from range-derived data provided by the radar system during the first period.
According to a further feature of the present invention, the approximate range-derived data is derived by extrapolation based upon an assumption that a speed of the given target derived from radar measurements during a latter portion of the first period remains constant.
According to a further feature of the present invention, the performance limitation criterion is additionally evaluated using target direction information related to a direction from the aircraft to the given target, wherein the target direction information is derived, at least during the second period, from tracking information provided by the missile seeker.
According to a further feature of the present invention, the evaluating is performed, at least during the second period, by a processing system located within the missile.
According to a further feature of the present invention, an audible indication audible to a pilot of the aircraft is selectively generated, dependent upon results of evaluating the at least one performance limitation criterion.